Dimethyl acetylenedicarboxylate → Dimethyl 3-ethyl-5-methoxyphthalate

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Reaction Steps

The following is based on the procedure described in Tam, T. F. and Coles P., Synthesis, 383 (1988). 6-ethyl-4-methoxy-2H-pyran-2-one (40.5 g, 263 mmol) was placed in a 500 mL round bottom flask and dimethylacetylenedicarboxylate (42 mL, 342 mmol) was added. This mixture was stirred until the solid completely dissolved. The flask was fitted with a water condenser and placed in a preheated oil bath at 180° C. for 3 hours. The reaction was allowed to cool to room temperature, diluted with dichloromethane (75 mL), and was purified by silica gel chromatography using a gradient of 5-20% ethyl acetate in hexanes. The appropriate fractions were collected and concentrated by rotary evaporation to yield compound P (44.16 g, 67%) as a clear oil. 1H NMR CDCl3 δ: 7.30 (d, 1H, J=3 Hz), 6.95 (s, 1H, J=3 Hz), 3.90 (s, 3H), 3.88 (s, 3H), 3.85 (s, 3H), 2.64 (q, 2H, J=8.0 Hz), 1.21 (t, 3H, J=8.0 Hz). ESMS m/z: 221 [M−OCH3]+, 275 [M+Na+].

Provenance & Evidence